Integrated circuit chip and fabrication method

ABSTRACT

An integrated circuit chip includes a substrate die and integrated circuits and a layer incorporating a front electrical interconnect network formed on a front face of the substrate die. A local electrical connection via made of an electrically conductive material is formed in a hole of the substrate die. The via is linked to a connection portion of the electrical interconnect network. An electrical connection pillar made of an electrically conductive material is formed on a rear part of the electrical connection via. A local external protection layer at least partly covers the electrical connection via and the electrical connection pillar.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional from United States Application forpatent Ser. No. 13/304,823 filed Nov. 28, 2011, which claims priorityfrom French Application for Patent No. 1061355 filed Dec. 30, 2010, thedisclosures of which are hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates to the field of semiconductor devices and,more particularly, that of integrated circuit chips and theirfabrication methods.

BACKGROUND

Integrated circuit chips are known which are provided with electricalconnection means which comprise electrical connection vias for passingthrough the substrate on a front face of which are formed the integratedcircuits, in order to produce electrical connections at the rear, thatis to say, opposite the side where the integrated circuits are situated,these electrical connection vias being provided with rear electricalconnection pillars. The rear face of the substrate and the vias arecovered with a permanent passivation layer made of a photosensitivepolymer, through which the rear electrical connection pillars are formedby using non-permanent conductive layers on this passivation layer.Consequently, the fabrication methods implemented comprise a largenumber of steps in particular because of the existence of thepassivation layer. Furthermore, the passivation layer cannot completelyfill the central hole remaining in the vias even though there is a riskof internal oxidation of the electrical connection vias.

SUMMARY

According to one implementation, a fabrication method is proposed thatat least partly avoids the abovementioned drawbacks.

A method for producing an electrical connection means of an integratedcircuit chip is proposed that comprises a substrate die and, on a frontface of the substrate die, integrated circuits and a layer incorporatinga front electrical interconnect network.

The proposed method may comprise: producing at least one localelectrical connection via made of an electrically conductive material,passing through the substrate die and linked to a connection portion ofsaid electrical interconnect network; producing an electrical connectionpillar made of an electrically conductive material, on a rear portion ofthe electrical connection via; and producing an external localprotection layer at least partly covering the electrical connection viaand the electrical connection pillar.

The proposed method may comprise: producing a hole through the substratedie via its rear face, revealing a connection portion of said electricalinterconnect network; producing, by a physical vapor phase deposition(PVD), a thin layer made of an electrically conductive material, abovethe rear face of the substrate die and the wall and the bottom of thehole; producing, by a local electrochemical deposition with electricalcontact on said thin layer, a local thick layer made of an electricallyconductive material on the thin layer, in the hole and above the rearface of the substrate die; producing, by a local electrochemicaldeposition with electrical contact on said thin layer, a rear electricalconnection pillar on the thick layer; and removing the thin layer aroundthe thick layer, the remaining portion of the thin layer and the thicklayer forming an electrical connection via linked to said frontinterconnect network and provided with the rear electrical connectionpillar.

The method may comprise: producing, by a chemical deposition, anexternal local protection layer at least partly covering the electricalconnection via and the rear electrical connection pillar.

The method may comprise, before producing the thin layer: producing aninsulating layer on the rear face of the substrate die and against thewalls of the hole; and removing a part of the insulating layer situatedabove said connection portion of the front electrical interconnectnetwork.

The method may comprise: producing the insulating layer by asub-atmospheric chemical vapor phase deposition (SACVD).

According to one embodiment, there is proposed an integrated circuitchip comprising a substrate die and, on a front face of this substratedie, integrated circuits and a layer incorporating a front electricalinterconnect network.

A proposed integrated circuit chip may comprise at least one rearelectrical connection means comprising an electrical connection viapassing through the substrate die and linked to a connection portion ofsaid front electrical interconnect network and comprising a rearelectrical connection pillar formed on the electrical connection via,and a local rear protection layer at least partly covering theelectrical connection via and the electrical connection pillar.

The electrical connection pillar may be provided, on its end, with adrop of solder.

The electrical connection via and the electrical connection pillar maycomprise copper (Cu) and the protection layer comprises an alloy ofcobalt (Co), tungsten (W) and phosphorus (P).

BRIEF DESCRIPTION OF THE DRAWINGS

An integrated circuit chip and an integrated circuit chip fabricationmethod, according to a particular embodiment of the present invention,will now be described as non-limiting examples, illustrated by thedrawing in which:

FIG. 1 represents a partial cross-section of an integrated circuit chip;

FIG. 2 represents a wafer of integrated circuit chips; and

FIGS. 3 to 10 represent steps in fabricating integrated circuit chips,seen in cross section.

DETAILED DESCRIPTION OF THE DRAWINGS

As illustrated in FIG. 1, an integrated circuit chip 1 comprises asubstrate die 2, for example made of silicon, on a front face 3 of whichare produced integrated circuits 4 and which is provided, on this frontface 3, with a front layer 5 in which is incorporated a front electricalinterconnect network 6, possibly with several metallic levels,selectively linked to the integrated circuits 4.

The integrated circuit chip 1 comprises a plurality of rear electricalconnection means 7, each of which has the following structure.

Through the substrate die 2, and in a region free of integrated circuits4, a hole 8 is formed which is prolonged (extended) in the front layer 5to an electrical connection portion 9 of the front interconnect network6. This connection portion 9 may be situated in the first metallic levelof the front interconnect network 6.

An insulating layer 10, for example made of silicon oxide (SiO₂), has apart 10 a which covers the lateral wall of the hole 8 and a part 10 bwhich covers the rear face 11 of the substrate die 2.

A local electrically conductive barrier layer 12, for example made oftitanium (Ti), in a bilayer of titanium nitride and titanium (TiN/Ti),of tantalum (Ta) or of a bilayer of tantalum nitride and tantalum(TaN/Ta), has a part 12 a which covers the part 10 a of the insulatinglayer 10 and the connection portion 9, in the bottom of the hole 8, andhas a local part 12 b which locally covers the part 10 b of theinsulating layer 10, over at least a part of the periphery of the hole8.

A local electrically conductive attach layer 13, for example made ofcopper (Cu), has a part 13 a which covers the part 12 a of the barrierlayer 12 and a local part 13 b which covers the local part 12 b of thebarrier layer 12.

A thick local electrically conductive layer 14, for example made ofcopper (Cu), has a part 14 a which covers the part 13 a of the attachlayer 13 and a local part 14 b which covers the local part 13 b of theattach layer 13. The part 14 a of the thick layer 14 determines aremaining central blind hole 15 which is open towards the rear.According to a variant embodiment, the thickness of the local thicklayer 14 may be sufficient to completely fill the rest of the hole 8 andthus eliminate the central blind hole 15.

An electrically conductive pillar 16, protruding towards the rear, forexample made of copper (Cu) is formed on the local part 14 b of thethick layer 14, this pillar being, for example, cylindrical.

On the end of the protruding pillar 16, a drop of electricallyconductive solder 17 is formed, which is, for example, made of an alloyof tin and silver (SnAg) or an alloy of tin, silver and copper (SnAgCu).

Finally, a local external rear protection layer 18, for example made ofan alloy of cobalt, tungsten and phosphorus (CoWP), comprises a part 18a which covers the part 14 a of the thick layer 14, in the remaininghole 15, comprises a part 18 b which covers the local part 14 b of thethick layer 14, around the protruding pillar 16, comprises a part 18 cwhich covers the flanks or lateral edges of the local part 14 b of thethick layer 14, of the local part 13 b of the layer 13 and of the localpart 12, as far as the part 10 b of the insulating layer 10, andcomprises a part 18 d which covers the peripheral face of the protrudingpillar 16 and, possibly, the drop of solder 17.

Thus, each rear electrical connection means 7 comprises an electricalconnection via 7 a formed by the layers 12, 13 and 14 and comprises theprotruding pillar 16, the end of which can be soldered to anotherelectronic component via the drop of solder 17, this via 7 a and thispillar 16 being protected against corrosion by virtue of the existenceof the external protection layer 18.

With reference to FIGS. 2 to 10, there now follows a description of amethod for collectively fabricating a plurality of integrated circuitchips corresponding to the integrated circuit chip 1 of FIG. 1.

As illustrated in FIG. 2, there is, for this, a wafer 100, for examplemade of silicon, having a plurality or matrix of placements 101 eachcorresponding to an integrated circuit chip 1 to be fabricated.

As illustrated in FIG. 3, integrated circuits 4 and front electricalconnection network 6 are produced in a common front layer 103, on afront face 102 of the wafer 100 and respectively in the placements 101.

Next, as illustrated in FIG. 4, pluralities of holes 8 are produced, viathe rear face 104 of the wafer 100 and respectively in the placements101 of the chips to be fabricated, by etching through correspondingthrough passages 105 a formed in a mask 105, and as far as portions 9 ofthe electrical connection networks. Then, the mask 105 is removed.

Next, as illustrated in FIG. 5, using a sub-atmospheric chemical vaporphase deposition (SACVD), an insulating layer 106 is produced on therear face 104 and in the holes 8 of the wafer 100, and the parts of thislayer 106 in the bottom of the holes 8 are removed so as to reveal theportions 9 of the front electrical connection network 6. The insulatinglayer 10 is thus obtained, in each of the placements 101 and for eachchip to be fabricated.

According to a variant embodiment, it would be possible to produce theholes 8 close to the portions 9 of the electrical connection networks 6,in the layer 103, then deposit the insulating layer 106, then remove theparts of this layer 106 in the bottom of the holes 8 and remove the restof the layer 103 to reveal the portions 9 of the front electricalconnection networks 6.

Next, as illustrated in FIG. 6, a layer 107 is produced by a physicalvapor phase deposition (PVD), on the insulating layer 106 and in thebottom of the holes 8, followed by a layer 108 on this layer 107, bothintended for the fabrication of the layer 12 then the layer 13 of thechips to be fabricated.

Next, as illustrated in FIG. 7, a mask 109 is formed on the layer 108,through which are formed openings 109 a, the edges of which correspondto the edges of the rear parts 14 b of the local layers 14 associatedwith the holes 8 of the chips to be fabricated. Then, an electrochemicaldeposition in a bath is used to produce the local layers 14 in theopenings 109 a of the mask 109, by making electrical contact on theperipheral edge of the layer 108, at the periphery of the wafer 100.

Next, as illustrated in FIG. 8, after having removed the mask 109, a newmask 110 is formed on the layer 108 and on the local layers 14, byforming, through this mask 110, through openings 110 a corresponding tothe pillars 16 to be produced on the rear parts 14 b of the local layers14 produced. Then, an electrochemical deposition in a bath is used toproduce the pillars 16 and then the drops of solder 17 in the openings110 a of the mask 110, by making, as previously, electrical contact onthe peripheral edge of the layer 108, at the periphery of the wafer 100.

Next, as illustrated in FIG. 9, after having removed the mask 110, a wetetch in suitable baths is used to remove the parts of the layer 108 thenthe previous layer 107, around the rear parts 14 b of the local layers14 produced, over all the remaining surface of the insulating layer 106.Local layers 12, 13 and 14 are then obtained which are associated witheach of the holes 8 of the chips to be produced.

Then, a bake is performed for the drops of solder 17 to assume the domeshape.

Thus, pluralities of local rear electrical connection means 7 areformed, in the placements 101 of the wafer 100, each comprising anelectrical connection through via 7 a and a protruding pillar 16provided with a drop of solder 17.

Next, as illustrated in FIG. 10, a naturally selective chemicaldeposition is used to produce protection layers 18 on the rearelectrical connection means 7. For example, if the thick layer 14 andthe protruding pillar 16 are made of copper, the protection layer 18 maybe formed by a selective chemical deposition of a ternary alloy based oncobalt, tungsten and phosphorus (CoWP) according to a self-catalyticvapor phase growth method.

Next, as illustrated in FIG. 2, the integrated circuit chips 1 obtainedin the placements 101 are singularized, for example by sawing alonglines 111 and columns 112 separating these placements 101.

The present invention is not limited to the examples described above.Many other variant embodiments are possible, without departing from theframework defined by the appended claims.

What is claimed is:
 1. An integrated circuit chip, comprising: asubstrate die; integrated circuits and a layer incorporating a frontelectrical interconnect network on a front face of the substrate die; atleast one rear electrical connection structure comprising: an electricalconnection via passing through the substrate die and linked to aconnection portion of said front electrical interconnect network; a rearelectrical connection pillar formed on the electrical connection via;and a local rear protection layer at least partly covering theelectrical connection via and the electrical connection pillar.
 2. Thechip according to claim 1, wherein the electrical connection via and theelectrical connection pillar comprise copper (Cu) and the protectionlayer comprises an alloy of cobalt (Co), tungsten (W) and phosphorus(P).
 3. The chip according to claim 1, wherein the electrical connectionpillar is provided, on its end, with a drop of solder.
 4. The chipaccording to claim 1, wherein the electrical connection via includes aportion on a back face of the substrate die which is offset from a holein which the electrical connection via is formed, said electricalconnection pillar formed on said portion of the conductive via locatedon said back face of the substrate die which is offset from said hole,said rear electrical connection pillar extending perpendicular to saidback face of the substrate die.
 5. The chip according to claim 1,wherein the electrical connection pillar is in the shape of a solidcylinder.
 6. An integrated circuit chip, comprising: a substrate die;integrated circuits and a layer incorporating a front electricalinterconnect network on a front face of the substrate die; a conductivevia extending from a back face of the substrate die to make electricalcontact with the front electrical interconnect network, said viaincluding a portion on said back face of the substrate die which isoffset from a hole in which the conductive via is formed; a rearelectrical connection pillar formed on said portion of the conductivevia located on said back face of the substrate die which is offset fromsaid hole, said rear electrical connection pillar extendingperpendicular to said back face of the substrate die; and a protectionlayer which at least partly covers the electrical connection pillar andsaid portion of the conductive via located on said back face of thesubstrate die which is offset from said hole.
 7. The chip according toclaim 6, wherein the electrical connection via and the electricalconnection pillar comprise copper (Cu) and the protection layercomprises an alloy of cobalt (Co), tungsten (W) and phosphorus (P). 8.The chip according to claim 6, wherein the electrical connection pillaris provided, on its end, with a drop of solder.
 9. The chip according toclaim 6, wherein the electrical connection pillar is in the shape of asolid cylinder.
 10. An integrated circuit chip, comprising: a substratedie having a front face with integrated circuits and a rear face; alayer on the front face incorporating a front electrical interconnectnetwork; a hole in the rear face which extends through the substrate dieto a surface of a connection portion of the front electricalinterconnect network; an insulation layer covering the rear face of thesubstrate die and sidewalls of the hole; a local electrical connectionvia in said hole made of an electrically conductive material that passesthrough the substrate die and is linked to said connection portion; anelectrical connection pillar made of an electrically conductive materialon a rear portion of the local electrical connection via; and anexternal local protection layer at least partly covering the localelectrical connection via and the electrical connection pillar.
 11. Thechip according to claim 10, wherein the electrically conductive materialis copper and the protection layer is an alloy of cobalt (Co), tungsten(W) and phosphorus (P).
 12. The chip according to claim 10, wherein theelectrical connection pillar is in the shape of a solid cylinder.